The at least two-component mortar compositions, used for the chemical fastening technique, generally contain a resin, which can be cured by free radical polymerization, in the one component, that is, the resin component (component “A”). Said resin is, for example, an unsaturated polyester resin, an epoxy acrylate resin or a urethane methacrylate resin, which may be dissolved in a copolymerizable reactive diluent, such as styrene or monomeric methacrylates. Aside from the resin, this resin component usually contains further additives, such as accelerators, inhibitors and the like, as well as fillers or thickening agents.
The second, necessary component of such a mortar composition for the chemical fastening technique, that is, the curing agent component (component “B”) contains the free radical-forming agent, such as a peroxide or an azo compound, which is required for the polymerization of the curable resin. Since the amount of free radical-forming agent, required for the free radical polymerization of the resin component, is much less than the amount of resin in the resin component and, moreover, since the free radical-forming agents, namely peroxides, can decompose explosively, the curing agent component usually contains a carrier material or desensitizing agent, with which the volume of the curing agent component is brought to a reasonable value and the danger of exploding the free radical-forming agent is decreased.
Finally, it is possible to provide even other constituents, which react chemically with the resin component and the curing agent component, in one or more further components, in which these constituents present are separated from one another so that a premature reaction cannot occur.
When used in the proper manner, the components, namely the resin component and the curing agent component, present in separate containers such as multi-chamber containers, are mixed immediately before use, particularly by being pressed out of these containers and passed through a static mixer for mixing the constituents, after which the mixture obtained is brought into the borehole in the solid substrates. Subsequently, the fastening element, such as an anchor rod, a connecting reinforcement, reinforcing steel or the like is introduced and adjusted, before the mortar composition is cured by polymerization of the resin in the presence of the free radical-forming agent.
During the mixing of the curing agent component with the resin component, problems arise owing to the fact that, as a rule, the amount of curing agent, that is, of free radical-forming agent, such as the peroxide, is much less than the amount of the resin in the resin component. This makes the homogeneous mixing of these two constituents, required for achieving constantly good and reproducible strength values, considerably more difficult. On the other hand, certain free radical-forming agents, such as dibenzoyl peroxide, are solid, so that the curing agent component, as a rule, contains a diluent, in order to dissolve or disperse the free radical-forming agent and, overall, to increase its volume, so that it can be mixed more easily with the resin component. In this connection, volume relationships of resin component to curing agent component of 7:1 to 1:1 and preferably of 3:1 to 1:1 are preferred. Consequently, however, liquid carrier materials must be added to the curing agent component in amounts, which cannot be disregarded, in order to achieve this volume relationship.
According to the state of the art, so-called desensitizing agents, which, on the one hand, act as diluents and, on the other, avoid undesirable decomposition of the free radical-forming agents, are used to adjust the flowability and concentration of the free radical-forming agent in the curing agent component or the volume of the curing agent component. Various types of unreactive plasticizers, for example, dicarboxylate esters such as dioctyl phthalate and dioctyl adipate, or polyesters, have already been used as desensitizing agents. In this connection, reference is made to the DE-A-32 26 602 and the EP-A-0 432 087.
In the WO 94/19397, reactive constituents, such as liquid epoxides or isocyanates, which are incorporated in the resin matrix during the curing of the mortar composition, are proposed as desensitizing agents. On the other hand, the DE-A-42 31 161 discloses an organic/inorganic hybrid system, which enables water to be used as desensitizing agent. In both cases, however, a suitable reactant for the reactive carrier medium of the curing agent component is required in the resin component, since the desensitizing agents, known from the state of the art, cannot be incorporated by the free radical polymerization in the network formed.
A further disadvantage of the aqueous hybrid system consists therein that a curing agent component, formulated on this basis, can be used only at temperatures, which are not very far below 0° C., since such a component freezes easily, so that its use at a building site in the open is limited.
It has now turned out that the conventional formulations for forming curing agent components of such an at least two-component mortar composition for the chemical fastening technique are not fully satisfactory either because amounts of carrier materials, which adversely affect the strength properties of the cured mortar composition, must be introduced, or because additional constituents, which react with the carrier material of the curing agent components, must be added to the resin component, and that, furthermore, the stability of the conventional curing agent components, particularly with respect to the decomposition of the free radical-forming agent, is unsatisfactory.
It is therefore an object of the present invention to indicate a curing agent component for an at least two-component mortar composition for the chemical fastening component, with which not only it is possible, in a simple manner, to introduce the small amount of free radical-forming agent in the desired volume of a carrier material in such a manner, that the required flowability and concentration of the free radical-forming agent is achieved, a high stability of the curing agent component is ensured and, at the same time, no or only little additional material is introduced into the mortar composition, as a result of which better strength properties of the cured mortar composition are ensured.
It has turned out that this objective surprisingly can be accomplished owing to the fact that, aside from the free radical-forming agent, the curing agent component contains water and a water-soluble, ethylenically unsaturated polyalkylene glycol derivative, which can be co-polymerized with the organic resin component.